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Plan to open dams could restore migrations of fish

by Katie Shaddix last modified June 24, 2008 12:46 PM

Alabama's great fish migrations ended the year man first walked on the moon. When the gates closed on the new Alabama River dam at Millers Ferry in 1969, an ancient connection between the Cahaba River and the Gulf of Mexico was severed, and a multitude of fish and mussel species began a long, slow spiral that could mean extinction for some. Now, on the heels of a similar effort in Georgia, federal and state regulators and a coalition of environmental groups are working on a plan to restore Alabama's lost migrations by helping the fish get around dams. They hope to reconnect the Cahaba to the Gulf by next year, pushed into action by declines for some species so severe that there is concern those populations may never rebound.

Plan to open dams could restore migrations of fish

Sunday, May 25, 2008

By BEN RAINES and JEFF DUTE

Staff Reporters

Alabama's great fish migrations ended the year man first walked on the moon.

When the gates closed on the new Alabama River dam at Millers Ferry in 1969, an ancient connection between the Cahaba River and the Gulf of Mexico was severed, and a multitude of fish and mussel species began a long, slow spiral that could mean extinction for some.

Now, on the heels of a similar effort in Georgia, federal and state regulators and a coalition of environmental groups are working on a plan to restore Alabama's lost migrations by helping the fish get around dams. They hope to reconnect the Cahaba to the Gulf by next year, pushed into action by declines for some species so severe that there is concern those populations may never rebound.

The problems in Alabama were compounded with the addition of the Claiborne Lock and Dam in 1971. Annual spawning migrations involving tens of millions of fish disappeared overnight, with the twin dams blocking more than a dozen species from moving upstream just as surely as dams out West have nearly wiped out the Pacific Ocean's salmon runs.

Success in Georgia

This year in Georgia, however, fish are once again migrating past the Woodruff Dam and moving hundreds of miles inland thanks to a solution so simple and easy it's a wonder it took decades to come up with it.

Instead of fighting for millions of federal dollars to build a complicated system of fish ladders, the U.S. Army Corps of Engineers agreed to open the navigation locks twice a day to let fish swim past the dam on their upstream journey. The locks are designed to let barges move past the dams, but, it turns out, they work just as well at moving fish.

"We're running the lock a couple of times a day. We'll open the lower gates, let the fish in, raise the water level and let them out the other side," said Steve Herrington, a Nature Conservancy biologist who helped come up with the lock plan. "The stories of the old-timers are not exaggerations. We've been living with depressed fish populations for the last 30 to 40 years. This is an idea that could get us back where we used to be."

The two dams between the Gulf and the Cahaba River are run by the corps.

Before the dams, the Alabama shad made annual runs through the Mobile-Tensaw Delta into the Alabama River and all the way upstate into the Cahaba and its tributaries, often returning to the small creeks they were born in, according to scientists. The shad runs numbered in the millions.

Disappearing fish

Nowadays, the Alabama shad has nearly disappeared from Alabama and was recently labeled a "Species of Greatest Conservation Need" by federal fisheries officials.

But it wasn't just the state's namesake shad that moved up the rivers each year. Mooneyes, stripers and redhorse suckers made their own runs hundreds of miles inland, alongside marine fish including mullet, needlefish and skipjack herring. Mullet still make it up into the Cahaba each year, according to scientists, but they are measured by the handful, not by the millions as they used to be.

Then there were the giants of the river, the prehistoric paddlefish with its gaping, bucket-sized mouth and the state's two sturgeon — the Gulf sturgeon and the Alabama sturgeon. All three species have suffered serious population declines, with the known number of Alabama sturgeon down to a single fish.

Scientists believe sturgeon, like a dozen other species, would benefit greatly from a return to their traditional spawning ground. Available spawning habitat had been reduced by 50 percent or more after the dams, according to scientists.

The return of millions of migrating fish would also be a boon for the state's incredibly diverse mussel populations, as the freshwater shellfish are dependent on fish to complete their spawning cycle.

The energy link

Scientists say many of the state's rivers have suffered another kind of decline after the dams, this one involving biological productivity. They likened the situation in those Alabama rivers to what is seen in rivers that are home to salmon migrations, where the annual return of fish from the sea acts almost like a big shot of biological fertilizer into the creeks and rivers where they spawn.

"We have cut the energy link. Here you've got a shad, an oily species that has a high energy value as a prey species," said Scott Herrington, a Nature Conservancy biologist. "Those shad are down there in the Gulf eating their hearts out, and we've cut the link that used to allow them to swim all the way up the Cahaba. They used to bring all that energy upstream where it ended up in the crawfish, the bass, all the species up the river."

Stan Cook, Alabama's chief of freshwater fisheries, said state officials have been trying to figure out how to get fish past the dams for years to, "allow fish species to reach their native spawning grounds and improve their status."

"As it often does, it came down to funding when we talked about fish passage in the late'90s," he said. "Then, the discussion was centered more on fish ladders or bypass structures and fish elevators. There hadn't been much study done on the effectiveness of locking the fish through."


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